SAN JOSE — A day that began with a pre-dawn bloodbath at a Cupertino cement plant grew into a massive manhunt that spread through a residential neighborhood in Sunnyvale, where SWAT teams in heavy body armor swept from house to house, frantically looking for the killer.

By the time darkness fell Wednesday, three people were dead, seven more had been treated for gunshot wounds at area hospitals and the suspected shooter, Shareef Allman, remained at large.

Allman, a 47-year-old heavy equipment operator at Lehigh Hanson”s Permanente Cement Plant, had been in a safety meeting with more than a dozen co-workers when, police say, he pulled a gun from his waistband and began shooting. One of the survivors of the shooting told the Mercury News that Allman felt co-workers were trying to have him fired after he was repeatedly accused of driving recklessly at the quarry.

The shooting spree set in motion a daylong manhunt along the Homestead Road corridor separating Cupertino and Sunnyvale. Schools went into lockdown or told students to stay home, and residents watched police helicopters hover over the neighborhood and nervously tried to figure out if the gunman might be in their backyard.

With search dogs winding through creeks and around schools, the manhunt continued into the night.

“Overnight we”ll continue to search for the suspect using the tips we get,” Sheriff Laurie Smith said. “We know the area that we searched is clear. Adjoining neighborhoods, please lock your doors, like you do every night. … We still believe the suspect is armed and extremely dangerous.”

Smith issued a plea for Allman to peacefully surrender. So did some of his friends, including some of the South Bay”s most prominent black leaders who described him as a peacemaker who campaigned against domestic violence and mentored troubled youth.

“This is not the Shareef that we know,” said Jethroe “Jeff” Moore II, head of the Silicon Valley NAACP.

The long day began at 4a.m. in a trailer where workers and supervisors met each morning. Allman took a stance he had practiced at area shooting ranges, where he often went with his .40-caliber handgun. Then he methodically moved down a line of coworkers, firing at each one until they fell, then moving to the next as if he were taking target practice, authorities said.

Authorities identified the dead as Mark Munoz, 59, of San Jose, John Vallejos, 51, of San Jose, and Manuel Pinon, 48, of Newman, all employees of Lehigh.

“He pulled out a Glock and just shot everybody and kept on shooting,” said Mike Ambrosio, 45, a union shop steward who was shot in the arm.

Allman then retrieved an AK47 he had brought with him to the quarry, apparently intent on settling grievances over his safety record as a truck driver at the plant. Then, when the shooting stopped, he disappeared into the darkness in a 1999 Mercury hatchback, until shortly before 7 a.m., when he abandoned his car at a Pho restaurant on Homestead Road.

Shortly before 7 a.m., Craig Corfield, a tennis pro who lives in the neighborhood across the street from what will eventually be the new Apple headquarters, heard three loud bangs. “I didn”t know they were gunshots, but I thought, ”That sounded funky,”” Corfield said. “Ten minutes later I heard sirens, and five minutes after that I walked out of our garage and there were helicopters everywhere.”

According to police, Allman attempted to commandeer the car of a woman in the parking lot of a Hewlett-Packard campus on Homestead Road, shooting her in the arm, but failed to get her car.

By 7 a.m., he had melted into the neighborhood along the Cupertino-Sunnyvale border, where for the rest of the day, sheriff”s deputies and SWAT teams from around the South Bay roamed the streets in heavily armored vehicles, searching every house and yard with the help of bloodhounds.

“The search dogs were able to get a scent from the car but they were handicapped by the rain,” the sheriff said.

Just before 10 a.m., Liz Houle stood in her driveway as a police helicopter swooped low over the street. Minutes earlier, two officers wearing flak jackets and toting automatic weapons climbed over a fence and clambered down to Calabazas Creek, which runs directly behind the Houles” home. Two of the family”s children were rushed off to school by their father, Phil, but the other two were marooned inside the dragnet because their school was locked down.

After monitoring a neighborhood message board all day, the Houles saw a SWAT team right outside and decided it was time to go. “It was getting kind of crazy. Some of the neighbors were saying it feels like a war zone,” Liz Houle said. “People are definitely nervous.”

Schools in Santa Clara, Cupertino and Sunnyvale closed or kept their students in a lockdown, some well past the regular end of the school day. But schools are expected to be back to normal today.

By Wednesday afternoon, police had recovered a shotgun, handgun and two assault rifles, some from Allman”s abandoned car. But Smith presumed that Allman was still armed.

Many residents in the area received reverse 911 calls warning them to stay indoors, and authorities cautioned that Allman had little to lose.

The manhunt kept Grace Chu of Fremont from getting to a baby-sitting assignment with her grandson. When she arrived around 8 a.m., she couldn”t get past the police blockade, so she called her daughter. “She”s right in the middle of it,” Chu fretted. “I”m a little worried. She didn”t even know what was going on when I called her.”

Allman”s neighbors at Stonegate apartments in North San Jose described him as a likeable, sharp-dressed guy, a single parent who goes to church and works out a lot. Several said he was a former semi-professional boxer. Neighbors said they never saw him do anything violent. All expressed shock when they learned he was suspected in a mass shooting.

Neighbor Albert Salazar, 51, said he had known Allman a long time. He spoke to him three days ago and didn”t notice anything unusual. They talked about growing up under hard circumstances and how they turned their lives around.

“It makes no sense,” Salazar said.

Wayne Riley went to high school with Allman”s daughter. “He was a good parent. He was always doing something to take care of his kids,” Riley said. “I do not know what happened.”

Many of his neighbors used to watch the community TV show Allman produced on San Jose”s cable CreaTV, and saw him as a successful entrepreneur. In a videotaped interview, Allman talked about a book he wrote to empower women against domestic violence.

“I”m a father and raised a daughter from birth,” Allman said in the interview, “and growing up in that type of environment and seen men abuse women, I said I can do something as an individual to make a difference.”

Outside the cement plant, relatives of workers gathered at police lines, hoping to find out if their loved ones survived the shooting. At midmorning, with dozens of family members anxiously awaiting word, one woman screamed and fell over backwards in a faint.

A light rain began to fall at one point, then at almost exactly the time Allman was attempting a carjacking several miles away, a rainbow appeared over the two besieged communities.